Circular saw blades have been in use for a long time and generally consist of a circular disk with cutting teeth formed into or attached to the periphery of the disk and a bore formed at the center of the disk to allow the mounting of the blade on the arbor of the circular saw. Very early circular saws were driven by water and steam and were massive stationary machines, but now circular saws may be portable light weight machines for easy, convenient use by a single person,
Similarly, early circular saw blades were unitary blades and were manufactured from a single piece of material, generally steel, wherein the cutting teeth were formed into the steel disk and were sharpened. Today, typically circular saw blades are composite blades that are manufactured from several materials for example, a steel disk with a plurality of carbide cutting teeth attached thereto. The steel selected for the disk typically has properties such as high strength, good manufacturability and low cost and the carbide selected for the teeth typically has properties such as high hardness, high abrasion resistance and good toughness. The finished circular saw blade then has the excellent overall properties of sharp, hard teeth on an inexpensive tough disk. Generally the carbide teeth are bonded to the steel disk by means of soldering or brazing.
In operation, circular saw blades are used to cut materials such as wood. The blade is rotated often at very high speeds in excess of 160 mph at the circumference. The hard teeth engage, cut and displace the wood. The displaced wood (chips) may pile up in front of the advancing tooth in the gullet until the time that the tooth exits the work piece and the chips are thrown from the gullet. Continued rotation of the blade directs the tooth around to engage the wood; the tooth passes back through the path cut in the work piece and around further to where it engages the work piece again to repeat the process until the cut has been completed.
It was recognized by those skilled in the are that the area of contact between the blade and the work piece should be kept to a minimum. This helps to reduce the amount of friction between the blade and the work piece. This minimized contact is realized through clearance gaps and clearance angles. Accordingly, some prior art circular saw blades have been designed with these objectives in mind.
Some prior art circular saw blades include teeth that are bent outwardly from the disk, in the case of a unitary circular saw blade. Alternatively in the case of composite circular saw blades the teeth are attached to the body where the teeth have a width greater than the body. Another common feature is the bevel to the top surface of the tooth, generally one tooth being bevelled to the one side and the next tooth being bevelled to the other side in an alternating top bevel pattern popular with blades used in cross cutting wood. A tooth that does not have a bevel to its top surface has a flat top surface and is aptly called a flat top tooth popular with blades used in ripping wood. In use some of the circular saw blades described above end up having sharp points at the ends of the cutting edge and under further use these points undergo a high degree of wear and often suffer breakage in use.
One example of a prior art circular saw blade is U.S. Pat. No. 4,222,298 issued Sep. 16, 1980 to James. This patent is directed to a circular saw blade with removable and replaceable teeth. The teeth are mounted on a slight angle (negative rake angle) so as to allow clearance between the rearward portions of the teeth and/or the securing nut and for the lobes of the blade and the piece of lumber being cut. These saw blades are clearly very large blades likely adapted for use in a saw mill. Accordingly since the circular saw blade described therein is clearly directed to one with removable teeth the orientation and position of the teeth is limited and therefore James could not be adapted to position the teeth to take advantage of clearance angles and cutting angles.